1. Field of the Invention
The present invention relates to an anti-reflection film producing method and apparatus. More particularly, the present invention relates to an anti-reflection film producing method and apparatus in which anti-reflection film can be produced with hard coat layers with high quality in an easy manner.
2. Description Related to the Prior Art
An optical film as an optical element is used as a main component for image display panels, for example, LCD (liquid crystal display), PDP (plasma display panel), ELD (electroluminescence display panel) and CRT (cathode ray tube). The optical film according to well-known techniques includes a transparent support, an optical functional layer, and a protective layer with physical strength. The protective layer operates to keep a high resistance to scratches for the optical film. Materials and combinations of the layers are selectively determined, to construct various types of optical films, such as an anti-reflection film, anti-glare film, optical compensatory film, surface producing film and the like.
The anti-reflection film is used for the purpose of raising clear display property suitable for recognition of the display panel. As the display panel is observed directly by human eyes, failure of appearance of the anti-reflection film, such as color defects and color unevenness, should be suppressed. Required quality of the anti-reflection film has become higher and higher according to the tendency of a larger screen size, higher brightness and higher precision in the field of the display panel.
Important properties of the anti-reflection film include the resistance to scratches, resistance to abrasion, a dust-proof property of small possibility of residual fingerprint, mark of water droplets or the like in consideration of the use for an image display. The resistance to scratches among those is important because irrecoverable defect occurs with scratches of the display surface to lower the image quality of the image display panel. In view of this, JP-A 9-145903 discloses an example of the anti-reflection film of which a low refractive index layer is positioned as an outer layer, and is formed from an optically curable resin composition, and contains fine particles, for the purpose of high resistance to scratches.
In general, the anti-reflection film is formed by applying a coating of a predetermined solution to a support, and by drying a layer of the coating. In addition to the high quality of the coating layer, high productivity is important by means of reduction of the production time or the like. To this end, a coating solution is prepared by mixture of compounds for the functional layer and an organic solvent, for the purpose of facilitating the application of the coating and of shortening the drying time. However, the coating layer immediately after the coating is fluctuated or unevenly dried by shock or vibration in the transport or by an unwanted air flow, so unevenness in the thickness of the coating layer will occur to cause failure in the appearance.
WO-A 2005-063484 (corresponding to JP-A 2005-257786) discloses suggestion for imparting high resistance to scratches and the high dust-proof property and also with high productivity of the anti-reflection film. A coating layer in the anti-reflection film of this document contains additives and fine particles of hardenable resin, fluorine compounds, silicone compounds and the like having a surface activity. Ionizing radiation is applied to the coating layer to form the low refractive index layer.
Also, a multi layer structure of the anti-reflection film is widely used, and includes a support, a hard coat layer and the low refractive index layer. A property of high adhesion on interfaces between the layers is required for the purpose of anti-reflection effect by preventing scatter of light. JP-A 2003-311911 discloses production of the anti-reflection film of which adhesion between the layers can be tight. For a layer next to the support, a hardenable resin having a reactive functional group is used. Also, hardening condition is adjusted.
It is possible according to JP-A 9-145903 and 2003-311911 to obtain the anti-reflection film having high resistance to scratches and high adhesion on interfaces between the layers. However, dust-proof property and productivity cannot be high. The techniques of all of those three documents have a problem of occurrence of powder-like white material on the surface of the protective layer over the optical functional layer to lower the quality of the appearance. It is impossible according to the prior art to produce the anti-reflection film with high resistance to scratches and reduced failure in the appearance also at a high productivity.